Beneficial Insects 



The larvae (Fig. 18, Plate IX, Page 27) are common among aphid 

 colonies. When first hatched they devour these soft bodied insects at 

 the rate of four or five a day and at the rate of twenty or more a day 

 when fully grown. Because of the numbers of plant-lice they devour, 

 these spindle-shaped larvae are called aphis-lions. 



In feeding, the aphis-lion seizes its prey in its long jaws, which are 

 so formed that each pair makes a tube through which the body contents 

 of the aphid are sucked up. 



During its existence as a larva the lace-winged fly probably con- 

 sumes from 300 to 400 plant, lice.* 



Many other small insects are eaten besides aphids. In the article 

 referred to in the preceding paragraph, the author lists ten insects be- 

 sides several species of plant-lice as hosts of the green lace-wing of Cali- 

 fornia. Among these are mites, leaf-hoppers, scale insects, mealy-bugs 

 and psyllids. 



When the larvae are fully grown they spin a white globular cocoon 

 (Fig. 17, Plate IX, Page 27), within which the pupal stage is spent. The 

 adult escapes by gnawing the end of the cocoon partially off and pushing 

 this up as shown in the figure. 



As there are several generations of the lace-winged fly each season 

 their importance as destroyers of injurious insects is difficult to estimate. 



6. WASPS 



(a) DIGGER-WASPS 



(Figs. 16, 17 and 18, Plate VI, Page 21) 



We are so accustomed to considering wasps as creatures of quickly 

 aroused temper who resent any trespassing in the vicinity of their nests 

 by stinging the intruder, that many an innocent and beneficial member 

 of the wasp tribe is summarily put to death and as a result many a crop 

 pest continues its work of devastation. 



There are fourteen families of digger-wasps in America north of 

 Mexico. Many of the members of these render invaluable service to the 

 farmer and gardener by destroying the insects feeding upon his crops. 

 In habits many of these represent a class intermediate between the true 

 predators, such as the ground beetles, and the true parasites, which will 

 be discussed later. 



(a-1) FAMILY SCOLIIDAE 



One member of this family, Tiphia inornata, which has been pre- 

 viously mentioned, burrows into the ground in search of white grubs, 

 upon which it lays its eggs and upon which the larvae are parasitic. 



These wasps are shining black and about three-fifths of an inch long. 



(a-2) SPIDER-WASPS 



Most of the members of this family dig burrows in the ground which 

 are stocked with spiders upon which the young wasps feed. A few spe- 

 cies, however, build cells of mud which are fastened under stones and in 

 other secluded places. 



(a-3) THREAD-WAISTED WASPS 



The wasps of this family can be distinguished from those of the pre- 

 ceding ones by the long slender first segment of the body. The peculiar 



"V. L. Wildermuth. "California Green Lacewing Fly." Journal ofiAgricultural Research. Vol. VI. 

 No. 14 (1916). 



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